The Krr1 protein of Saccharomyces cerevisiae is involved in processing of pre-rRNA and assembly of pre-ribosomal 40S subunits. To further investigate the function of Krr1p we constructed a conditional cold sensitive mutant krr1-21, and isolated seven genes from Schizosaccharomyces pombe whose products suppressed the cold sensitive phenotype of krr1-21 cells. Among the multicopy suppressors we found genes coding for translation elongation factor EF-1α, a putative ribose methyltransferase and five genes encoding ribosomal proteins. Using the tandem affinity purification (TAP) method we identified thirteen S. cerevisiae ribosomal proteins interacting with Krr1p. Taken together, these results indicate that Krr1p interacts functionally as well as physically with ribosomal proteins. Northern blot analysis revealed that changes in the level of krr1-21 mRNA were accompanied by similar changes in the level of mRNAs of genes encoding ribosomal proteins. Thus, Krr1p and the genes encoding ribosomal proteins it interacts with seem to be coordinately regulated at the level of transcription.
It was found that wild type yeast Pichia pastoris can tolerate vanadate concentration as high as 25 mM in the growth medium. Moreover, four vanadate-resistant P. pastoris strains designated JC100/1, JC100/3, JC100/9 and JC100/15 exhibiting tolerance up to 150 mM vanadate were selected. Growth of P. pastoris was correlated with vanadate to vanadyl reduction and its accumulation in the growth medium. In two selected strains, JC100/9 and JC100/15, protein kinase A activity was much higher in comparison to the wild type strain even without vanadate addition to the growth medium. Moreover, in the presence of vanadate, protein kinase A activity was significantly increased in the wild type and the vanadate-resistant JC100/1 and JC100/3 strains. It was also found that phosphorylation of a 40 kDa protein associated with ribosomes occured in all vanadate-resistant strains from the logarithmic, while in the wild type strain from the stationary growth phase. From the presented results it can be concluded that a protein kinase A signalling pathway(s) might be involved in the mechanism of P. pastoris vanadate resistance. The results also indicate a possible role of the 40 kDa protein in protection of P. pastoris against vanadate toxicity.
What is the microbe that we are dealing with? Whether it is cholera or anthrax, we want to know the disease-causing microorganism as quickly as possible since prompt identification of the causative organism would help control disease spread - and potentially save lives through provision of appropriate care and medication. Yet, despite the advent of rapid microbial identification tools – particularly those based on mass spectrometry – most undergraduate curricula continue to focus on culture- and nucleic acid-based identification techniques since they are widely used for detecting and identifying microbes in clinical and environmental samples. Mass spectrometry-based methods, however, have increasingly complemented traditional approaches in clinical and research laboratories - but are rarely featured in undergraduate curricula. Motivated by the desire to address the curriculum gap, the author of this study developed an inquiry-based laboratory exercise for introducing students to the operating principles and methodology of mass spectrometry-based microbial identification. By requiring students to identify microbes in environmental water samples – a real-life problem with unknown answers – the exercise piqued the students’ interest in learning, while helping to stir their curiosity through an interesting field activity in which they could put on a scientist’s hat in solving a mystery. This synopsis article summarizes a piece of published educational research and expands on the discussion of concepts underlying matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based microbial identification. Herein, the article discusses the relative advantages and disadvantages of the pattern recognition and proteome database search approaches for analyzing mass spectra data. Additionally, the effect of general and tailored sample preparation protocols on identification accuracy is also elaborated. Finally, the pedagogical utility of field- and inquiry-based educational tools is also discussed in greater detail from a post-publication perspective. A full-length synopsis of the work and a structured abstract can be found in the accompanying PDF file, the original article being entitled: “Teaching Microbial Identification with Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) and Bioinformatics Tools”.
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